The invention relates to improvements in shock absorbers in general, and more particularly to improvements in shock absorbers with variable damping characteristics. Such shock absorbers can be utilized with advantage in many types of vehicles.
Commonly owned copending patent application Ser. No. 031,252 filed Mar. 26, 1987 by Werner Komossa and Peter Brand, now U.S. Pat. No. 4,765,445 granted Aug. 23, 1988, and commonly owned German Offenlegungsschrift No. 36 05 182 of Dirk Wessel disclose shock absorbers wherein a cylinder contains a piston which divides the internal space of the cylinder into two chambers. The piston is reciprocable by a piston rod which extends through one end wall of the cylinder, and the piston has one or more passages for the flow of a damping fluid between the two chambers in response to axial movement of the piston rod relative to the cylinder and/or vice versa. In addition, the piston is formed with one or more bypasses and carries electrically operated valves which regulate the flow of damping fluid between the chambers by way of such bypasses.
The valving elements of the regulating valves slide relative to their seats and/or other parts of the respective valves with attendant generation of friction which can affect the accuracy and predictability of the damping operation. As a rule, the valving elements slide along cylindrical surfaces. It has been found that, when the pressure of damping fluid in the cylinder reaches a very high value, e.g., in the range of 50 bar, friction between the valving elements and the adjacent parts can adversely influence the reaction time of the valves. In other words, friction can adversely influence the timing of movement of valving elements from closed to open positions or vice versa as well as the speed of movement of the valving elements between such positions. The problem is aggravated as the pressure in the interior of the cylinder increases. In fact, elevated pressures can cause actual jamming of the valving elements so that the flow of damping fluid through the bypasses cannot be regulated at all.